Comparative studies were performed to evaluate the growth and fecundity of earthworm, Eisenia foetida, in the combination of cattle manure and rice straw with different C/N ratios under laboratory condition. The observations indicated that the biomass of E. foetida was significantly higher in cattle manure with C/N ratio of 21.8 and 80% cattle manure +20% rice straw with C/N ratio of 24.9 when compared to other treatments at 30, 60, 90 days. Moreover, the population of worms in 60% cattle manure+40% rice straw, which had a C/N ratio of 28.7, was significantly greater than that of others at 60 or 90 days, and the number of worms increased up to 324 after 90 days. The C/N ratio of vermibeds showed significantly negative relation with earthworm biomass and population. In conclusion, the optimum C/N ratio of cattle manure and rice straw combination is from 21.8 to 24.9 for E. foetida growth, and 28.7 for fecundity.